DIRECTIONS OF VIBRATORY MOVEMENT. 365 
Number of cases in which houses moved measurable distances on their foundations in 
different directions, and average distance moved. 





Total moved and 
: pa sneer by 
i A N b f A dist direction. Avers list 
cae le crea) caueatony SUSPMT ANI SAP deal atiascs 
Per cent 
of total. 
NW. ol 1.19 
SW. 39 1.05 84 69 11 is 
W. 14 1.36 
NE. 6 1.91 
SE. 14 1.29 29 24 1.39 
E. 9 122 
N. 4 2:37 
S. 5 ‘30 f ? é ee 
Rotaler. 122 1.24 




Southwest-northeast, 45=37 p. ct. of total; northwest-southeast, 45=37 p. ct. of total. 
The entire number moved in first three and opposite directions was 113, or 93 p. et. of total. 
INTENSITIES. 
The houses covered by this study may be grouped in three divisions, according to 
locality: those on the hills at Burlingame and San Mateo heights; those at Belmont, 
Homestead, and San Carlos, which are partly on the level valley land and partly on the 
low hills; and those at San Mateo and Redwood City, on the valley-floor. The data 
indicate strongly that the intensity of the shock was less on the hills than on the flat, 
in spite of the fact that the houses on the hills were nearer the fault-line. In fact, several 
houses on the rock-formed hills very near the earthquake fracture did not give evidence 
of any greater intensity than those at San Mateo. 
The Buri-Buri Ridge, as the hills are called, is composed of an old and very much 
compacted series of sedimentary rocks, sandstone, shale and jasper, and of serpentines. 
Moreover, they are not deeply covered with soil, so that they form a strong foundation 
for the houses. 
The percentage of houses that moved on their foundations on the hills was 6 per cent; 
and at Belmont, etc., 3 per cent moved, as against 27 per cent at San Mateo and Red- 
wood City. ‘This is shown in the table on page 355. Among the very few houses that 
shifted on the hills and in the Belmont region, only 4 or 5 moved an appreciable dis- 
tance, while in a majority of cases in the valley the movement was considerable. 
From the figures given in the table on p. 356 it appears that of the chimneys, 73 per 
cent fell on the hills, 88 per cent in the intermediate settlements, and 92 per cent in the 
valley. The intensity of the shock, as shown by the amounts of falling of dishes and 
cracking of plaster, was greater in the flat country. The following table gives the per- 
centage in these cases. Of course the classification of the damage is very arbitrary 
and the figures at best are but indicative. Of cases recorded in which furniture failed 
to move appreciably in houses, 90 per cent were on the hills. 
Degrees of damage to plaster and household articles on hills and low lands. 

San Mateo AnD REDWOoD. Bretmont HItts, ere, 

AMOUNT OF DAMAGE, 
Slight. | Medium.| Great. | Slight. |Medium.| Great. 

Percentage in cases of crack- 
ing of plaster; °°. ~. 40 30 30 79 11 10 
Percentage in cases of falling 
of dishes, etc., in varying a2 | 




Amount” 9 FL! Sr ke. ets 40 20 40 74.3 23.3 





